The author, superintendent of the Essex County Hospital, has prepared this manual primarily for the benefit of the neophyte psychiatric witness who is called on to testify as an expert before a tribunal. Recognizing that the psychiatrist is 'playing in the lawyer's arena and plays by lawyers' rules, taking the law as he finds it', the author makes no pretense at legal or psychiatric profundity, nor does he consider the problem of interdisciplinary 'fit'; rather, he emphasizes what the witness should do or say if he wants to help a party at interest in an adversary procedure. This goal presupposes a superficial knowledge of pertinent points of law, the preliminary steps, including details of examining a patient, which are necessary to prepare testimony, the format of the testimony itself, and the various pitfalls and booby traps that await the unsuspecting physician. There is stress throughout on typical attitudes of judges,